Paranthropus robustus, a dead-end branch of the early human family tree, has been described as a "chewing machine" that was mostly jaws and not much brains.
While the label may still apply, pioneering dental detective work has revealed unexpected news about the species' dietary variety.
Using lasers to vaporize tiny particles of tooth enamel, researchers in the United States and Great Britain analyzed the chemical makeup of 1.8-million-year-old fossil teeth from four individuals unearthed in the Swartkrans cave site in South Africa.
Different types of edible plants leave unique chemical signatures in living tissue, including teeth.
Based on the types of carbon isotopes preserved in the P. robustus fossils, the team concludes that the diminutive primates had a surprisingly varied and flexible menu.
Their seasonally adapted diet may have included fruits, seeds, roots, tubers, and even insects.
The findings contradict the long-held theory that P. robustus was a dietary specialist that chomped solely on low-quality plants, the researchers report in tomorrow's issue of the journal Science.
Scientists had long cited this theory to explain why the bipedal primate went extinct 1.5 to 1 million years ago, arguing that the human ancestor couldn't cope with food scarcity in Africa's changing environment.
(Related news: "Tooth Study Reveals Diets of Early Humans" [August 3, 2005].)
But the new study suggests a different story.
"Lucy's Children"
Standing just four feet (about a meter) tall and weighing about a hundred pounds (45 kilograms), P. robustus appeared in East Africa about 2.5 million years ago.
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